Osteoarthritis of the Knee Learning Center

Understanding Osteoarthritis (OA) of the Knee

Don't let knee pain keep you on the sidelines. It's time to get back into the life you enjoy.

When your knee aches continually from erosion of the joint and its internal padding, your life may come to a standstill. "And that's not good, for a host of physical and psychological reasons," says Mary I. O'Connor, M.D., associate professor and chair, department of orthopedic surgery at the Mayo Clinic in Jacksonville, FL. "Usually, the muscles around the knee provide cushioning and support while you walk or run. But, if you have to dramatically reduce your level of activity to avoid knee pain, then the muscles of the leg will weaken."

These weaker muscles, she points out, provide less cushioning to the knee—and the pressure of each step has to be absorbed mainly by that joint. As a result, your OA may become even worse, setting up a cycle of pain, inactivity and further joint erosion. "On top of that," she adds, "as you become less active because of pain, it's easy to become frustrated and depressed."

Osteoarthritis (OA) can occur in almost any of the body's 200 or so joints, but OA of the knee is the most common type, accounting for more than 5.5
million doctor office visits annually in the United States. That's because the knee, with all the demands placed on it to bend, twist and straighten, is vulnerable to injury.

Most people who suffer from OA of the knee are older than 55, and about half of them are over 65; in fact, knee OA is one of the leading causes of disability among older men and women. According to the American Academy of Orthopaedic Surgeons (AAOS), the risk of disability from OA of the knee is equal to that of cardiovascular disease. "While I have 75-year-old patients who are physically active and don't consider themselves to be old," says Dr. O'Connor, "patients who are younger, but suffer from knee OA, often admit to feeling old and incapacitated."

In one survey, when adults with knee OA were asked how they felt most of the time during the previous month, more than 10 percent said that every activity was an effort, with many expecting their health to worsen, along with their morale. "Luckily there are a host of things that can be done to change this outlook," says Dr. O'Connor.

What's Happening?

"Osteoarthritis typically begins in knees that have experienced trauma, infection or injury," says Richard Iorio, M.D., professor of orthopaedic surgery at Boston University School of Medicine. The cartilage that acts as a protective cushion between the bones starts to wear down. This decreases the ability of the cartilage to work as a shock absorber to reduce the impact of stress on the knees. Over time the remaining cartilage wears down faster, and in some spots it eventually may disappear altogether, leaving the bones to grind against one another.

"In addition, the joint slowly changes shape," adds Dr. Iorio, "and this causes more pain, swelling, stiffness and a decrease in motion at the joint." The formation of osteophytes, or spurs—tiny growths of new bone that the body generates in an attempt to repair knee damage—can add to discomfort as they rub against nearby nerves and bone.